1. Field of the Invention
The present invention relates to an organic light emitting display and a method of driving the same, and more particularly, to an organic light emitting display in which brightness is restricted in accordance with an emission area and the amount of change in the brightness varies with the emission area and a method of driving the same.
2. Discussion of the Background
Light emitting displays may be classified as either organic light emitting displays, which use organic light emitting diodes (OLED) and inorganic light emitting displays, which use inorganic light emitting diodes.
An OLED includes an anode electrode, a cathode electrode, and an organic emission layer positioned between the anode electrode and the cathode electrode. The organic emission layer emits light by combining electrons and holes.
An inorganic light emitting diode, referred to as a light emitting diode (LED), includes an emission layer formed of inorganic material such as a PN-junction semiconductor.
FIG. 1 illustrates the structure of a conventional organic light emitting display. Referring to FIG. 1, the conventional light emitting display includes a pixel unit 10, a data driver 20, a scan driver 30, and a power source supply unit 40.
The pixel unit 10 includes a plurality of pixels 11, each of which is connected to an OLED (not shown). The pixel unit 10 also includes n number of scan lines S1, S2, . . . , Sn-1, and Sn arranged in a row direction to transmit scan signals, n number of emission control signal lines E1, E2, . . . , En-1, and En arranged in a row direction to transmit emission control signals, m number of data lines D1, D2, . . . , Dm-1, and Dm arranged in a column direction to transmit data signals, m number of first power source supply lines (not shown) for transmitting a first power source ELVdd, and m number of second power source supply lines (not shown) for transmitting a second power source ELVss with a lower potential than the potential of the first power source ELVdd.
The brightness and duration of emission of light emitted by the OLEDs in the pixel units 10 are controlled to display images by the scan signals, the emission control signals, the data signals, the first power source ELVdd, and the second power source ELVss.
The data driver 20 applies data signals to the pixel unit 10 through the data lines D1, D2, . . . , Dm-1, and Dm.
The scan driver 30 sequentially outputs the scan signals to the specific rows of the pixel unit 10 through the scan lines S1, S2, . . . , Sn-1, and Sn. The scan driver 30 sequentially outputs the emission control signal lines to the specific rows of the pixel units 10 through the emission control signal lines E1, E2, . . . , En-1, and En.
The data signals and scan signals are transmitted to the pixels 11 to generate a current that corresponds to the data signals. The currents flowing to the OLEDs are controlled by the emission control signals. When the scan signals and the emission control signals in all of the rows are sequentially selected, one frame is completed. Images are thus displayed by the emission of light from the OLEDs.
The power source supply unit 40 transmits the first power source ELVdd and the second power source ELVss to the pixel unit 10. The second power source ELVss has a lower potential than the first power source ELVdd. Currents corresponding to the data signals thus flow through the pixels 11 due to the difference in voltage between the first power source ELVdd and the second power source ELVss.
Organic light emitting displays such as the one described above require a large amount of current to flow through the pixel unit 10 for the pixel unit 10 to emit bright light and require a small amount of current to flow through the pixel unit 10 for the pixel unit 10 to emit dim light. A large load is applied to the power source supply unit 40 to produce enough current to produce bright light, which requires the power source supply unit 40 to have a high output capability.
The widths of the emission control signals may be used to control the brightness by controlling the amount of time during which light is emitted. However, when the brightness is low, the amount of time that the light is emitted may be so short that a viewer may perceive a flickering phenomenon.